Automatic telephone system.



A. H. DYSON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATiON FILED OCT. 31, 1905.

Patented May 30, 1916.

7 SHEETS-SHEET I.

A. H. DYSON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED OCT. an 1905.

Patented May 30, 1916.

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7 SHEETSSHEET 2.

F N w INVENTOR WITNESSES A, H. DYSON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED OCT. 31. 1905.

Patented May 30, 1916.

7 SHEETSSHEET 3.

INVENTOR.

\AHTNESSEZSZ- A. H. DYSON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED OCT. 31, I905.

Patented May 30, 1916.

T SHEETS-SHEET 5.

nmmuulunn |n|| nu IIITIIIIIIIIII IIITIIIIIII I INVENTOR A. H. DYSON.

AUTOMATIC TELEPHONE SYSTEM.

INVENTOR 5 E S s E N W W A. H. DYSON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED OCT. 3|. I905.

Patented May 30,1916.

INVENTOR T SHEETSSHEET I.

ALFRED H. DYSON, or CHICAGo, ILLINOIS, AssIeNo'n, BY MESNE ASSIGNMENTS, TO KELLOGG SWITCHBOARD & SUPPLY COMPANY, A ConronA'rIon or ILLINOIS.

Specification of Letters Patent.

Patented May 30, 1916.

Application filed October 31, 1905. Serial No. 285,321.

To all whom it may concern:

Be it known that I, ALFRED H. DYsoN, a resident of the city of Chicago, county of Cook, and State of Illinois, have invented new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

My invention relates to telephone systems in which the interconnecting of subscribers lines is secured by means of electrically controlled switching mechanisms at the exchange, operating responsive to substation switching mechanisms controlled by the subscribers.

An object of my invention is to provide an organization of electrical circuits at the central exchange, using as few electromagnets as possible, thus securing a system of low initial cost and one that may be maintained at a comparatively low expenditure.

A further object is to provide an improved form of mechanical switch adapted for use in connection with the circuits of my invention.

As is well known, it has heretofore been the practice to employ in connection with the switching devices of automatic telephone exchanges, magnets in local circuits controlled by relays operated over the telephone lines, the relays serving merely to repeat the impulses sent over the lines to the magnets of the switches. This arrangement is employed because the magnets have relatively heavy work to do in adjusting the mechanical parts of the switch, and it would not be feasible to place their windings directly in circuit with the lines on account of the varying resistances of such lines. Were they so placed, it would be found that on long lines, conditions under which the magnets would operate would not permit them to properly perform their work.

The work required to be done by the relays operating over the line circuits is of an extremely exacting nature even when it 15 considered that their only work is to attract and release their armatures to close and break circuits through the magnets. This is because the impulses transmitted over the line come in quick succession, and unless a relay is very sensitive and rapid in its operation, it may happen that its armature will fail to be retracted at the conclusion of each and every impulse, the relay some times holding its armature up While two impulses are passing through it, which of course, results in transmission of too small a number of impulses to the magnet it is operating. It is thus seen that relays operated by the line impulses must be very carefully constructed, and after placed in operation must be kept very carefully tuned up and maintained in the highest possible state of efficiency and sensitiveness.

In the systems of automatic telephony hitherto known, it has been customary to provide one such relay for each selective switch in the exchange. In such systems where several switches are successfuly employed in completing one connection, one to select the thousands, another to select the hundreds and a third to select the units, for instance, three such relays will be brought into operation in completing each connection. In practising my invention however, in connection with'such systems as that before indicated, but one such relay would be used which would receive all the sets of current impulses transmitted from the substation and distribute them directly to the magnets of the various switches.

It has heretofore been the practice in the systems in general commercial use, to provide a first selector for each telephone line in the exchange, and a number of second selectors and connectors proportionate to the number of co-existing calls expected to occur at the busiest hour of the day. Assume a 10,000 line system of this character provided with facilities for 10 per cent. trunking, there would be 10,000 such relays operated by the line impulses described, one for each first selector; there would also be 1,000 such relays, one for each of the second selectors employed, and another 1,000 relays, one for each of the connectors, making a total of 12,000 relays each of which should be ready at all times to respond with absolute accuracy to the line impulses. In accordance with my present invention, I do away with first selectors individual to the subscribers lines, and provide means for interchangeably temporarily associating a limited number of such selectors with the different telephone. lines upon the initiation of calls at the substations. In a 10,000 line system with 10 per cent. trunking, I would therefore employ 1,000 first selectors, 1,000 second selectors and 1,000 connectors, and in addition, automatically controlled means whereby on the removal of a receiver at a substation, one of the first selectors will be brought into operative association with the calling line. This may be accomplished in any desired manner, and I do not wish to be limited to the particular means herein disclosed, consisting of a simple switch, one for each telephone line.

Associated with each first selector, I provide a relay adapted, when the first selector has been automatically associated with the calling line, to receive the directive impulses transmitted from the substation, said relay serving to re-transmit the impulses, first to the magnet of a first selector; after the adjustment of the latter,.to the magnet of a second selector, and after the adjustment of the latter, to the magnets of a connector, and thus in a 10,000 line exchange, but 1,000 relays of which is required the exacting service heretofore referred to are needed.

It will be 'noted that I not only do away with a large numberof relays heretofore used of which this particular service was required, but that in carrying out my invention, I also do away with a large num- -ber of relays heretofore used, one for each switch, for receiving impulses transmitted over the opposite side of the telephone line from that over which the directive impulses are transmitted. This I do by providing one such relay associated with the first selector, and employing it to receive all currents transmitted over the other line limb, above referred to.

I thus do away with a large, amount of apparatus and moreover, with the apparatus of a character particularly likely to give trouble in automatic telephone exchange systems and to cause a very heavy operating and maintenance expense.

These and other features of my invention will be more particularly described and pointed out in the general description and claims.

'Referring to the drawings, Figure 1, consisting of Sheets 1, -2 and 3, illustrates, in diagrammatic form, two substations connected by their respective telephone lines with the exchange, and circuits at the exchange for interconnecting them. Fig. 2 .is a side view of a private switch. Fig. 3- is a view of the wipers and contact bank of the said switch. Fig.4 is a sectional view, showing the arrangement of wipers and shaft. Fig. 5 illustrates a connector. switch. Fig. 6 illustrates detail of the off normal switching mechanism of the said connector switch. Fig. 7 is a sectional view of .a contact bank of. said switch. Fig. 8 shows the mechanism of a private magnet and a release magnet for said switch. Fig. 9 shows mechanism employed in the control circuit shown in Fig. 1. Fig. 10 is a top view of the circuit-changing springs shown in Fig. 9.

Fig. 11 is a sectional view of a connector.

switch, showing details of the primary magnet and its associated mechanism. Fig. 11 is a top view of a portion of the releasing lever for said switch. Fig. 12 is a side view of a connector switch, showing details of the secondary magnet and its associated mechanism. Fig. 13 illustrates a release magnet for a selector switch and its associated mechanism. Fig. 14 is a side view of a selector switch. Fig. 15 illustrates a detail of Fig. 8.

Referring first to Fig. 1, I show at A a substation circuit connected by limbs P and S of the telephone line with the private switch C at the exchange, which latter is individual to the telephone line and is operated by a preliminary switching movement at the substation. After being initially operated, its movement is independent of the substation. Associated with its wipers 42, 43 and 44, are a plurality of contacts similar to 48, 49 and 50, terminals of control circuits similar to D, each control circuit being connected with the circuit of a first selector switch common for connection to all subscribers.

One hundred private switches may be conveniently grouped together and ten control circuits assigned to them, multipled terminals of said circuits appearing before the wipers of each private switch. Thus, assuming a ten thousand line exchange, there would be one hundred groups of one hundred private switches each, and one hundred groups of control circuits of ten each.

The control circuit D is provided with relays 62 and 63, adapted to be operated by current impulses transmitted over the two limbs of the line and act as relays to transmit corresponding currents to the operating magnets of the first selector, second selector and connector switches. These relays are common for operating all three switches, and I am thus enabled to avoid the use of separate primary and secondary relays for each switch such as have hitherto been employed in systems of this character. A material saving in apparatus is thus secured, and the size of mechanical switches maybe reduced. The control circuit shown at D also comprises means for controlling the supply of talking battery which is supplied from a central source, apparatus for automatically ringing an idle called subscribers line and apparatus for controlling the release of the various switches used in the connection.

A first selector switch, the circuit of which is shown at E, may comprise wipers 122, 123 and 124 andmultipled terminals of one hundred second selector switches which may be divided into ten groups of ten switches each, the difierent groups being common different thousands of the exchange, assuming a ten thousand line exchange. The terminals of each group may be disposed in a section of contacts by itself. The circuits, shown at E, comprise means for causing wipers 122, 123 and 124 to execute primary movements, each movement bringing the wipers adjacent to a different section or group of second selector switch terminals. Said circuits also provide means for starting the wipers moving over the-terminals of a selected group, such movement being automatically controlled and arrested when terminals of an idle second selector switch are reached. Thus, 'a first selector switch may pick out a limited group of one thousand subscribers lines by selecting an idle second selector switch representing such a group.

A second selector switch, circuits of which are shown at F, may comprise wipers 160, 161 and 162 and terminals such as 163, 164 and 165 of one hundred connector switches, divided into groups of ten, each group being common for connection to a dilferent one hundred lines of the thousand of which the second selector switch is representative. The terminals of each group of connector switches may be disposed in a separate section. The circuit, shown at F, includes means for causing wipers 160, 161 and 162 to. select any one of these sections or groups of terminals of connector switches, and further means for causing the wipers to move over the terminals of a selected group, their motion being automatically controlled and arrested when they engage terminals of an idle switch. Thus, by means of the circuit shown at F, a second selector switch may be caused to pick out a limited group of one hundred subscribers represented by an idle connector switch, of the thousand.

A connector switch, the circuits of which are shown at G, may comprise wipers 197, 198 and 199and contacts, multipled terminals of one hundred subscribers lines adapted to be engaged by said contacts. The said 'contacts may conveniently be divided into groups of ten, according to their values in the hundred, the terminals of each group being placed ina separate section. The circuit, shown at G, includes means for causing wipers 197, 198 and 199 to select a desired one of these groups of ten, and further means for causing them to select any desired terminals out of such a group.

If wipers 197, 198 and 199 are brought to rest in engagement with contacts, terminals of a busy subscribers line, the calling subscriber receives the busy signal and, by replacing his receiver, disconnects the various switches. If the line of the called subscriber is idle, the bell of the called subscriber is automatically rung and his response operates to cut the ringing generator out of circuit. At the end of the conversation, the replacing, by either subscriber, of his receiver upon the hook operates upon control circuit D to effect the disconnection of all the switches used in establishing the connection.

This provision of means, by which all switches may be released from either substation, is believed to be new in a system of this character, employing a trunk release system.

The system, as a'whole, operates, as will be understood from the foregoing, upon the multiple trunk system, the principles of which are well known, and it will be understood that the numerical ratios suggested above may be varied to suit particular conditions.

The detail of the circuit arrangement of my invention will be best. understood from the following narrative of operation, reference being had to Fig. 1, the three sheets being placed in their numerical order, Sheet 1 being at the left.

Assuming that subscriber A desires to connect his line with the line of subscriber B, to whom is assigned number 3456, subscriber .A first removes his receiver from the hook lever, whereupon contact 8-9 is closed. Current thereupon flows from ground G at the exchange, over the heavy conductor to limb P, through the substation, through contact 89 and the transmitter, returning over limb S, over the other heavy conductor, through contact 44.-47, through electromagnet 23 to battery 203. Electromagnet 23 is energized and attracts armaturcs 25 and 27. Current flows from ground G through contact 2425, through contact 2930, through operating magnet 31 and to battery, the magnet attracting its armature to open contact 2)30, thus effecting its deiinergization. Magnet 31 vibrates its armature as long as contact 24-25 is closed, each. vibration efiecting a step-bystep movement of \vipres 42, 43 and 44. The first vibration of armature of magnet 31 eiiocts the closure of contacts 2019 and 1817. The closure of the first contact connects ground G to contact 200 and renders the line of subscriber A busy to incoming calls. The closing of contact 17-18 establishes a path for the flow of current from ground G through the said contact, through cut-off relay 37 to battery 203, the cut-off relay attracting its armatures to disengage anvils 39 and 41, thus opening circuit through wipers 43 and 44 and preventing interference with existing conversations while they are wiping over terminals of busy control circuits.

The first energization of magnet 31 causes wiper 42 to engage contact 45, thus closing circuit from ground G through the said contact, through contact 2726 to battery, locking electromagnet 23. This first movement of the Wipers does not open contacts 4346 and 4447, a second movement of the wipers being required to bring them to engage contacts, terminals of the first control circuit. This feature insures the operation of cutsoff relay 37 before the first control .circuit is reached. The second movement of the wipers causes them to engage contacts, terminals of the first control circuit. Should this be already in use, its contact, corresponding to contact 48, will be grounded from ground G of some other private switch by way of contact 27-28 of said switch; and electromagnet 23 of the private switch of subscriber A will continue energized, circuit being traced from the ground G of the other private switch referred to, through the winding of its electromagnet 36 to wiper 42 of the private switch of the subscriber A and through the winding of electromagnet 23 to battery. The resistance of electromagnet 36 to that of electromagnet 23 is so proportioned that the former does not attract its armature. Similar circuits will be successively established through electromagnet 23 until wiper 42 engages a contact, terminal of an idle control circuit. Such terminal will be ungrounded, electromagnet 23 will be deenergized, its armatures resume their normal positions shown in Fig. 1 and operating magnet 31 will cease to vibrate its armature, owing to the opening of contact 2425 which opening also opens circuit through cut-oil relay 37. The armatures of the latter again engage anvils 3.9 and 41 and circuit is closed from the limbs of the line of subscriber A to wipers 43 and 44.

1 Assuming the idle control circuit selected to be that shown at D, wipers 42, 43 and 44 are'now resting in engagement with contacts 48, 49 and 50 of the said circuit. The closing of contact 2827, upon the deenergization of electromagnet 23, connects ground G through the winding of magnet 36 and the said contact and wiper 42, to terminal 48 of the control circuit and its multiples so that the circuit .is rendered busy with respect to other private switches. Subscriber A now rotates dial 1 to the right until three teeth have passed below spring 3. When the dial is in other than normal position, the stop shown thereon allows contact 6-7 to open, separating the two limbs of the line, the return of the dial to normal operating to again close them. Subscriber A now releases the dial and it rotates from right to left, the three teeth referred to cl osing contact three times and causing three impulses of current to flow from ground G at the substation, through the said contact, over limb P of the line, over the heavy conductor, through contacts 43 49 and 5152, through the winding of primary relay 62 to the live side of battery 203.

Primary relay 62 is energized three times and three attractions and releases of its armature cause three impulses of current to flow from ground G, through contacts 58 57, 8786, 9293 (first selector switch E), contact 107106, through the winding of primary magnet 101. The three resulting energizations of the said magnet bring wipers 122, 123 and 124 adjacent to a section of contacts, terminals of second selector switches, assigned for connection to the third thousand group of subscribers lines. With the first primary movement of the wipers, contact 99100 is closed, to remain so until the switch is released; also, contact 9698 is broken and contact 97--96 is closed.

Referring now to the substation A, with the return of dial 1 to normal, a tooth thereon engages spring 4, momentarily closing contact 45, causing the flow of current from ground G through the said contact, over limb S of the line, through contacts 4041, 4450, 1416, through the winding of secondary relay 63 to battery 203. The attraction and release of the relays armature effects a flow of current from ground G through contacts 58-59, 9089, 94.95 at the first selector switch, through the winding of private magnet 110 to battery 210. Said magnet attracts its armatures, opening contacts 11l112 and 113-114 which remain open, due to the continued energization of the said magnet, as long as wipers 123 and 124 are wiping contacts, terminals of busy second selector switches. The closing of contact 117118, upon the energization of magnet 110, establishes a path for the flow of current from ground G through contacts 99100, 96-97, 117118, 120'121, through the winding of secondary magnet 119 to battery 210. The said magnet is energized and deenergized, owing to its vibratory circuit, and moves wipers 122, 123 and 124 to engage contacts, terminals of the first second selector switch of the group. With the first secondary movement of the wipers contacts 9293 and 94-95 are opened. I the first second selector switch is busy, its contact, engaged by wiper 122, will be grounded from ground G of another first selector switch, through its contacts 99-400, 9697, 117116, 104105, through its wiper 122, to a multiple of the contact engaged. Current will therefore flow from the grounded contact, through wiper 122 of switch E, through its contacts 105104 and 110115, through the winding of private magnet 110 to battery 210, thus locking the said magnet. Secondary magnet 119 will vibrate its armature, causing wipers 122, 123 and 124 to engage contacts, terminals of successive second .selector switches, until an idle switch is reached, successive locking paths for magnet 110 being established until an idle switch is reached. When this occurs, its contact, engaged by wiper 122, will be ungrounded, circu t through private magnet 110 will be opened, and its armatures will return to the positions shown in Fig. 1, the opening of contact 118-117 preventing further vibration by magnet 119 of its armature. Wipers 122, 123 and 124 therefore rest in engagcment with contacts, terminals of the idle second selector switch assumed to be switch F.

Subscriber A now transmits four impulses of current by means of dial 1, over limb P of the line, through primary relay 62 of control circuit D, and a similar number of impulses are transmitted by the said relay from ground G through contacts 58-57, 87-86, 111-112, 123-126, 128-129 (switch F), through contact 156-155, the winding of the primary magnet 151, to battery 210. Four primary movements of wipers 160, 161 and 162' are effected by the four resulting energizations of magnet 151 to bring the wipers adjacent to a section of contacts, terminals of connector switches assigned to the fourth hundred of the third thousand group of lines. With the first primary movement of the wipers, contacts 132-133 and 135-134. are closed; also, contact 136-138 is opened and contact 137-136 closed.

A single impulse transmitted from ground G with the return of the dial to normal, causes a single energization of secondary relay 63, which transmits a single impulse of current from ground G through contacts 58-59, 90-89, 114-113, 124-127, 131-130, through the private magnet 139 of switch F, and to battery 210. The said magnet is energized and attracts its armatures, opening contacts 140-141 and 146-147, which remain open until an idle selector switch is reached. Magnet 139 also closes contacts 142-143 and 144-145. The closure of the first contact causes a flow of current from ground G through contacts 133-132, 136-137, 143-142, 150-149, through secondary magnet 148 to battery 210, the magnet vibrating its armature and causing wipers 160, 161 and 162 to engage terminals of the first connector switch of the group. With the first secondary movement of wipers 160, 161 and 162, contacts 128-129 and 130-131 are opened and remain so until the switch is released. Should this switch be busy, a circuit will be established from ground G of another second selector switch rendering it busy, to a multiple of the contact engaged, through the contact and wiper 160 of switch F, through contacts 159-158 and 144-145 and the winding of the private magnet to battery 210. Secondary magnet 148 will continue to vibrate its armature, with each vibration moving the wipers to engage terminals of successive switches, successive locking paths for magnet 139 bein established until an idle connector switch 1s reached. ,When this occurs, assumed to be when wipers 160, 161 and 1.62 engage contacts 163, 164 and 165 of the connector switch G, the contact engaged by wiper 160 will be ungrounded, circuit will be broken through magnet 139, its armature will return to the posltion shown in the illustration and, owing to the resulting opening of contact 143-142, the further energization of electromagnet 148 is prevented and the wipers rest in engagement with the terminals of the idle switch. The closing of contact 143-144, with the deenergization of magnet 139, connects ground G through contacts 133-132, 136-137, 143-144, 158-159, through wiper 160 to terminal 163 and its multiples, rendering the selected connector switch busy.

Subscriber A new transmits five impulses of current from ground G through primary relay 62, which in turn causes five impulses to flow from ground G", through contacts 58-57, 87-86, 111-112, 123-126, 140-141, 161-164, 169-170 (connector switch G), through armature 175 and the winding of primary magnet 176 to battery 204. The five energizations of the primary magnet eti'ect five primary switching movements of wipers 197, 198 and 199, bringing them adjacent to a section of multiplied line terminals, including those of subscribers to whom are assigned numbers running from 3451 to 3460. With the first primary movement of the wipers, contact 166-167 is closed, to remain closed until the release of the switch. The return of the dial to normal causes a single energization of secondary relay 63, which causes an impulse of current to flow from ground G at circuit D, through contacts 58-59, 90-89, 114-113, 124-127, 146-147, 162-165, 172-171 at switch G, through armature 177, through the Winding of secondary magnet 178 to battery 204. A secondary movement of the Wipers is effected by the energization of the said magnet, but their normal positions are such, with respect to the contacts with which they are adapted to engage, that this first movement approaches them to the first contact of a selected row onlv. With the first movement of the wiper, contacts 170-169 and 171-172 are broken and contacts 169-168 and 172-173 are closed. Six impulses, now sent from substation A, cause six energizations of the primary relay 62 at circuit D, and a corresponding number of impulses are transmitted from ground G at the said circuit, over the previously traced path,through contacts 161-164, contact 169-168 at switch G, contact 181-180, through armature 177, through secondary magnet 178 to battery 204. Six energizations of the secondary magnet are caused, and the first of these brings wipers 197, 198 and 199 into engagement with the first terminal contacts of the selected group of lines, and thesixth into engagement with the sixth contacts of the group, or contacts 200, 201 and 202, terminals of the line of subscriber 3456, or subscriber B. Should the line be busy at this time, wiper 200 will be connected to ground G at switch H, should subscriber B be a calling subscriber, or to ground G at some other connector switch, should subscriber B be a called subscriber. A single impulse of current sent from ground G at substation A, by the energization of relay 63, will cause a single impulse to flow from ground G", over the previously traced ath, through contacts 162-165, 172-1 3, 185184, through the winding of electromagnet 192 to battery 204. Magnet 192 thereupon attracts its armature 193 to engage anvils 194 and 195.

- On the closing of contact 193, 194 ground at G will momentarily beconnected, over a circuit practically without resistance, to armature 193. If another connector G has already connected With the called line its relay 179 will be energized by a circuit extending from ground G through said relay 179, contacts 190189, 197-200, 1917, to battery through relay 37 of the called line. Resistance 361 is provided in order that current may not be momentarily nearly all shunted from relay 179 of the other 0on nector by a branch of the before traced circuit extending from multiple 200 engaged by Wiper 197 of the connector whose relay 179 is energized and to the before mentioned ground G. Said resistance serves merely to protect the relay 179 of such other connector.

Contact 200, engaged by Wiper 197, being grounded, as before mentioned, current flows from ground, through contacts 200197,, 189191, 193194, through electromagnet 192 to battery 204, locking the said magnet. Subscriber A, having at this time his receiver to his ear, will receive the busy signal from interrupter 196 at switch G, circuit being traced through double contact 1951931 94, through contact 184185, over the heavily marked conductor, through contact 8990, condenser contact 16-14, thence over the heavily marked conductor through the exchange, to limb S of the line, through contact 98 at the substation, returning over limb P of the line, over the heavily marked conductor contact 51, contact 52 and relay 62 to battery.

Being thus notified that the called line is busy, subscriber A replaces his receiver, arm 10, associated with hook lever 8, cooperating with springs 11, 12 and 13 to simultaneously ground the two sides of the line. Primary relay 62 and secondary relay 63 at switch D are simultaneously energized and their armatures attracted to close contact 5554. Current thereupon flows from ground G at private switch C, through the winding of release magnet 36, through contacts 28-27, 4248, 54---55, then over conductor 206, through the winding of release magnet 102 of the first selector switch, to battery 210. Release magnets 36 and 102 of switches C and E, respectively, are energized, preparatory to the return of the switches to normal. The energization of release magnet 102 attracts its armature 105 to establish a path for the flow of current from ground G at switch F, through release magnet 152, contacts 134- 135, 122, 105-103 to battery 210. Release magnet 152 is therefore energized, preparatory to the return of switch F to normal. It attracts its armature 159 to establish a path for the flow of current from ground G at the connector switch, through the winding of release magnet 174, contacts 167166, 163160, 159157, to battery 210. Release magnet 174 is energized, preparatory to the return of the connector switch to normal.

Referring to substation A, with the return of the hook lever to normal, arm 10 passes over the extremity of spring 11, springsll, 12 and 13 disengage, thus removing ground from the limbs of the line and causing the deenergization of relays 62 and 63. The. resulting opening of contacts 54 and 55 dei nergizes release magnet 36 of switch (J and 102 of switch E. The definergization of the latter magnet effects the dei nergization of release magnet 152 of switch F, which in turn efl'ects the dei nergization of release magnet 174 of switch G. The deenergizations of their respective release magnets cause the returns of the various switches to normal and their disconnection.

Returning now to the point at which wipers 197, 198 and 199 first engage contacts 200, 201 and 202, and assuming that the line of subscriber B is idle at this time. which is the condition shown in Fig. 1, it will be observed that contact 200 is connected, through contact 19-17 and the winding of cut-off relay 37, to the active side of battery 204. When electromagnet 192 is in this case energized, with the return of the substation dial to normal, the closing of contact 193-194, instead of cansing the establishment of a locking circuit for electromagnet 192, connects wiper 197 to the active side of battery 204; and contact 200 being also connected to the same side of the battery, electromagnet 192 is deenergized upon the cessation of the impulse transmitted from the substation. The release of its armature 193 causes arm 189 to disengage anvil 191 and to engage anvil 190. A path for the flow of current is thereby I established from ground G through relay 170, contacts 190-189, 197-200, 19-47,- through the winding of cut-ofl' relay 37 to battery 204, causing the encrgization of relay 37, which opens up the circuits of the line of subscriber B at his private switch. This flow also energizes electromagnet 179, which attracts its armatures 181 and 185, the former to engage anvils 182 and 183, the latter to engage anvils 186 and 187.. Current thereupon flows as follows: from ground Ur at switch G, through the upper winding of impedance coil 188, through contacts 183-181, 168-169, to the left over the heavily marked conductors, through contact 8687, contact between springs 57 and 56, through the winding of electromagnet 60, to the active side of battery 203. The resulting energization of magnet 60 moves arms 14, 51, 86 and 89 to engage contact points 15, 53, 88 and 91, respectively. Current thereupon flows as follows: from ground G at control circuit D, through the upper winding of differential relay 74, through the upper winding of relay 71 which is serially wound, then through contacts 65-06, 5351, 49-43, 3938, over limb P to substation A, through contact 89, through the substation transmitter, supplying current thereto energizing the same, through contact 7-6, returning over limb S, through contacts 4041, 4450, 1415, 6968, through the lower winding of relay 71, through the lower winding of differential relay 74 to battery 203. Relay 74 remains neutral. The relatively high resistance windings of relay 64 and of impedance 188 now in series are at this time shunted by the relatively low resistance windings of relay 74, and relay 64 does not attract its armatures. Relay 71 attracts its armature and current flows from ground G through contacts 7273, 7879, through the winding of ringing relay 83 to battery 203. The relay attracts its armatures, armature 81 operating to cut ringing generator 207 into circuit with the line of subscriber B, the our rent flowing from the said generator, over the heavily marked conductor through the exchange to limb P, through the condenser and bell at the substation, returning over limb S and over the other heavily marked conductor, through armature 82 and, the said armature being attracted, through winding 76 of relay 77 to battery 203. This being alternating current, relay 77 does not attract its armature.

When, however, subscriber B removes his receiver, which operates to close contact 9--8 at his substation, current flows from ground G at the battery control circuit to limb P of the line, through contact 8-9 at the substation, returning over limb S,

through armature 82, through winding 76,,the core of relay 74 is magnetized and armaof relay 77, to battery 203. This flow direct current causes relay 77 to attract its armature 80 to engage spring 78, thereby establishing a locking circuit for itself from ground G", through contact 7273. Subsequent tothe closing of contact 80-78, the movement of armature-80 opens contact 79-7 8, thereby deenergizing ringing relay 83, whose armatures resume their positions shown, establishing the talking circuit. Current now flows from ground G through the upper winding of relay 74, through the upper winding of relay 64, through armature 81, through contact 88 86, over the heavily marked conductor to the right, through the exchange to limb P of the line of subscriber B, over the limb, through contact 89, through the transmitter, supplying talking current thereto, through contact 76, returning over limb S, over the other heavily marked conductor through the exchange to the left, through contact 8991, through armature 82, through the lower winding of relay 64, through the lower Winding of relay 74 to battery 203. Relay 64 is serially wound and thisflow of current is of suiiicient volume to cause it to attract its armatures to close contacts 6766 and -69, opening contacts 65-436 and 68-69 at a .time subsequent to the closing of the first mentioned contacts. The switching operations described reverse the connection of ground G and the active side of battery 203 to the respective limbs of the line of subscriber A, ground G being'now connected through the upper winding of relay 74, the

upper winding of relay 71 and contact 7 O-69, and the heavy conductor, to limb S of the line of subscriber A, while the active side of battery 203 is connected to the lower winding of relay 74, the lower winding of relay 71, contact 6766 and the other heavy conductor, to limb P. Thus, the direction of the How of current in the line of subscriber A is, by the response of the called subscriber, reversed.

The two subscribers are now in conversation through condensers 84 and 85. It will be noted that the supply of current through both lines is through the windings of differential relay 7 4 a portion of the transmitter current supply for the called line being also fed tl'irough the windings of impedance coil 188. The flow through the two windings being of equal volume, the core is neutral. Either subscriber, however, may,

by grounding the two limbs of his line, un-

balance the neutralizing effect of the two windings and cause the magnetization of the core. Thus, when either or both subscribers, at the end of the conversation, replace their receivers, thus simultaneously grounding the two limbs of one or both lines at the substation, by the operation of arm or arms 11.

ture 209 is attracted, whereupon current flows from ground G armature 209, through the winding of control circuit release relay 61, to battery 203. Relay 61 attracts its armature to close contact 62 -63 and current flows from ground G at private switch C, through the Winding of release magnet 36, through contacts 28-27, 42-48, 63 -62 over conductor 206, through the Winding of release magnet 102 of switch E, to battery '210. Release magnet 36 of the private switch is energized, closing contacts 35-34 and 33-32. It also opens contact 21-22 and connects ground G to spring 22, whereupon current flows from ground G, through the winding of cut-01f relay 37 to battery 203. The cut-0E relay attracts armatures 38 and 40, opening circuit from wipers 43 and 44 to the line limbs, in order that, upon the release of the switch, the wipers may be open while wiping over busy contacts in their return to normal. Contact 22-21 is again closed when the switch reaches normal. The closing of contacts 32-33 and 34-35 mentioned is for the purpose of providing means for continuing the unbalancing effect of the two grounded limbs of the line of subscriber A upon the winding of relay 74, until ground is removed at the substation. Otherwise the energization of cut-ofi' relay 37 would prematurely' disconnect the line of subscriber A from the windings of relay 74.

Referring to E, the flow of current through release magnet 102 energizes, it, and contact 105-103 is closed, establishing a path for current from ground G through release. magnet 152, 134-135, 125-122, 105-103 to battery 210, energizing release magnet 152. The energization of release magnet 102 also effected the closure of contact 96-98 and the energization of magnet 110 by current flowing from ground G contacts 99-100, 96-98, and through the said relay to battery 210. The magnet 110 attracts its armatures, opening the circuit of wipers 123 and 124, the relay remaining energized until switch E returns to normal.

he energization of magnet 152 established a path for the fiow of current from ground G at switch G, through the winding of release magnet 174, contacts 167-166, 163-160, 159 157, to battery 210, causing the energization of release magnet 174. Magnet 152, when energized, also effects the closure of contact 136-138 and current flows from ground G through contacts 133-132, 136-138, through magnet 139 to battery 210. The magnet is energized and attracts its armatures, opening circuit through wipers 161 and 162, and remains energized till the return of the switch to normal. Release magnet 174 is energized, the energization causing to be opened, whereupon relay 179 is deenergized and its armatures are retracted to contact 189-190 open the circuits of wipers 198 and 199. When, in the course of the release operations, ground is removed from the limbs of the subscribers line, by which the unbalancin of the windings of relay 74 is being eii ected, or in case the subscribers are simultaneously replacing their receivers, ground is removed from the limbs of both lines, the core of relay 74 will be de-magnetized and armature 209 will be retracted. Its retraction opens circuit through release relay 61, and arms 14, 51, 86 and 89 return to the positions shown. Contact 62-63 is now opened and the circuit is broken through release magnet 36 of the private switch C. Its armature is released and contacts 32-33 and 34-35 are broken. With the-return of the switchs wipers to normal, contact 22-21 is again closed, and contacts 20-19 and 18-17 are opened, while contact 17-19 is again closed. Circuit is broken through cut-off relay 37, the retraction of whose armatures again connects wipers 43 and 44 with limbs P and S of the line. The opening of contact 62 -63 at circuit D also caused release magnet 102 at switch E to be denergized and the wipers of the switch to return to normal. lVith their return, contacts 92-93 and 94-95 are again closed and contact 99-100 is opened. The opening of the latter deenergizes magnet 110, and the relays armatures return to the positions shown. The denergization of magnet 102 also opens contact, 103-105, circuit being broken through release magnet 152 at switch F, and the magnet deiincrgized, whereupon the switchs wipers return to normal. With the return of the wipers to normal, contacts 128-129 and 130-131 are again closed. Also, contacts 135-134 and 132-133 are opened, the opening of the latter causing the deenergization of magnet 139, and the return of its armatures to the positions shown in the illustration. When magnet 152 is denergized, its armatures return to the positions shown, cont-act 159-157 is opened and, as a result, release magnet 174 at the connector switch is deenergized. This causes the return of the switchs wipers to normal, and with their return, contacts 172-171 and 170-169 are again closed, while contact 166-167 is opened. All apparatus, used in the connection, has now been restored to normal. I also provide means for enabling the calling subscriber, should he so desire, to release and disconnect whateverswitches he may have caused to be connected in the course of making the call. At any time after a control circuit has been selected by the private switch, by grounding the two limbs of the line, relays 62 and 63 will be simultaneously energized, closing contact 54-55. Current will then fiow from ground G at the private switch,

through contacts 28-27, 4248, 54-55, and through release magnet 102 of first selector switch E, to battery. The energizations of release magnets of other switches proceed as before. When ground is re moved from the two limbs at the substation, contact 5'-1-55 is broken, the various release magnets are deinergized. and disconnection proceeds as before. While I have shown a plurality of batteries in Fig. 1, they may be one and the same battery.

Referring now to Fig. 2, the mechanism there shown is adapted to perform the work of circuits C and H. The circuit changing springs shown in the said Fig. 2, are supplied with reference characters corresponding to the circuit drawings and their operation where effected directly by the armature mechanism of the electromagnets, will be obvious. I show a shaft 226 to which is attached ratchet 218, adapted to be rotated with each attraction of armature 215 of magnet 31 by the engagement therewith of pawl 217. Associated with ratchet 218 is detent 219,.which engages the teeth of the ratchet and holds it and the shaft in whatever rotated position they may be brought by the operations of pawl 217. Spring 19 has attached to it a lug Lug 224 is normally engaged by the extension of ratchet 218, the spring being held in the raised position shown thereby. \Vith its first movement, the ratchet disengages lug 224 and the spring moves downward, opening contact 19-17 and closing contact 1920. The electromagnets and their associated parts, shown in Fig. 2, may conveniently be mounted upon one side of a metal plate, upon the opposite side of which may be mounted contact bank 225. Shaft 226 extends through the mounting plate and supports wipers 42, 13 and 44, the arrangement of these parts being shown in Fig. 3. A sectional view, show ing mounting plate. wipers and shaft, is shown in Fig. 4, in which view is also shown spring 250. against the tension of which the shaft is rotated and which returns the shaft and wipers to normal when the switch is released.

Referring now to Fig. 2, when magnet 36 is energized, it attracts armature 222, which draws to the right spring lever 251. The latter, when drawn forward, engages lug 221. by means of an orifice such as shown in Fig. 11. When this occurs, carrier 220 is moved downward by tension of lever 251, and contact 2122 is opened and contact 22-22 is closed. Vhen the magnet is deenergized, armature 222 is retracted and lever 251 draws detent 219 out of engagement with the tooth of ratchet 218, in engagement with which it may have been placed by the operation of the switch. This allows ratchet 218, carrying with it shaft 226, to rotate in the opposite direction. As

it returns to normal, the ratchet again engages lug 224 upon spring 19, raising the spring upward and returning it and springs 17, 18 and 20 to normal. Ratchet 218 also engages carrier 220 on its return to normal moving the carrier upward, which causes spring 22 to again engage spring 21. The upward movement described also causes lever 251 to disengage detent 221, which returns to normal, resuming its supporting relation with lever 251.

Referring now to Fig. 12, I there show a side elevation .of a connector switch, including one section 255 of a. contact bank. In Fig. 7 is shown a sectional view of a bank on line 256257 of Fig.- 12. The terminal contacts of the bank are disposed as if projectigig through the inner surface of a hollow sphere, as will be apparent from an inspection of Fig. 7 and section 255, shown in Fig. 12. Referring to the said Fig. 12, the

wipers or contact arms of the switch may be rotated from left to right by means of shaft 226 to which ratchet 227 is attached, the said ratchet being rotatable by primary magnet 176, the details of this being shown in Fig. 11. Thus, the wipers may be rotated to positions in front of, and into engagement with, different sections of contacts similar to that shown at 255. A second shaft 235 is provided, adapted to be moved downward by the operation of secondary magnet 178, as indicated in Fig. 12. Upon the extremity of this shaft is a lug 236 which, as the shaft moves downward, presses downward the extremity of the wipers engaged by it. The ends of the wipers are so spaced with respect to the bank, that the first movement toward the bank only approaches them to it, With out causing their engagement with bank contacts. The wipers being pivotally associated with shaft 226, successive downward movements of shaft after the first, bring the wipers into engagement with successive sets of contacts of a selected section. There being the proper number of teeth on ratchet 227 and the proper number-of ratchet teeth in shaft 235, the contact end of the wipers may be brought to engage any of one hundred sets of contacts in a bank.

Referring to Fig. 5, it will be noted that lug 236, upon the end of shaft 235, is broad in order that primary movements may not bring end 237 of the wipers beyond the extremity of the lug.

Referring now to Fig. 11, the primary movements of the wipers are controlled as follows: Primary magnet 176 is provided with armature 232 to which is attached pawl 228. When the said magnet is energized, its armature draws the said pawl forward, the latter engaging a tooth of ratchet 227 and rotating the ratchet of the primary shaft one step from left to right. Detent 229is provided, associated with ratchet 227, and holds the ratchet in Whatever position it may be rotated. Detent 229 is normally held out of engagement with the ratchet, the first movement of armature 232 codperating with lever 231 to release the said detent, as will be hereinafter described. The ordinary circuit changes, directly'effected by the armatures of connector switch electromagnets, will be obvious in the illustration and will not be described. 7

Referring now to Fig. 5, attached to the rotary shaft is an arm 233 which, when the shaft is in its normal position, presses against buffer 234 and holds spring 166 out of engagement with spring 167. A top view of these parts is shown in Fig. 6. The first rotary movement of shaft 226 is in a direction to move arm 233 away from buffer 234 so that spring 166 engages spring 167. WVhen the primary shaft is released and returned to normal, the arm again engages the buffer and restores the springs to their normal positions. Assuming the rotary shaft has been stepped a sufficient number of times to bring the wipers of the switch opposite a desired section of contacts, their movement along the section to select desired contacts will lee-described, having reference to Fig. 12. Secondary magnet 178 is provided with armature 238, with which is associated pawl 239. With each movement of. the armature, said pawl engages a tooth on vertical shaft 235 and moves the shaft downward a step. Below the ratchet engaged by pawl 239 is a second ratchet, whose teeth detent 243 is adapted to engage. Detent 243 is normally out of engagement with its ratchet. The first movement of armature 232, acting upon lever 231 (Fig. 11), operates to release the said detent and cause it to engage the ratchet. The said detent engages, with each thrust of pawl 239, suc-.

cessive teeth of its appropriate ratchet and holds-shaft 235 in whatever downward position it may have been carried by a thrust of pawl 239. Attached to shaft 235 is arm 238, which, when the shaft is in its normal position, holds stud 265 .in the position shown in Fig. 5, whereby contacts 169170 and 171-172 are maintained closed. and contacts 169168 and 172-173 are maintained open. With the first downward movement of shaft 235, arm 238 is carried down so that stud 265, which extends through the frame of the switch, is carried downward by the tension of springs 169 and 172 and opens contacts 170169 and 171 172, closing contacts 169168 and 172173. When shaft 235 is released after the switch has been operated and returns to normal, arm 238 again engages stud 265, and the springs associated with it are returned to normal. Electromagnet 192 (see Fig. 8) is provided with armature 301, with which is associatedarm 302, provided with a lug toward its extremity. \Vhen magnet 192 is energized, its armature draws arm 302 to the left so that the lug thereon engages a buffer of insulating material, shown associated with spring 189. When the magnet is deenergized, its armature retracts arm 302, which carries with it spring 189, opening contact 189-191 and closing contact 189-- 190.. Release magnet 174, shown in Fig. 8, is provided with armature 304, associated with which are arms 305 and 306. \Vhen the magnet is energized, the latter of these arms, which is interlocked with arm 302, retracts the latter out of engagement with spring 189, whose tension again closes contact 189-491. Detail of this is shown in Fig. 15. A dog 360'is provided, its normal relatlon to arm 302 being such that when the arm is attracted, its solid right extremity is brought over dog 360. If, under this condition, release magnet 174 is energized, arm 306, depressing arm 302, causes dog 360 to engage the extremity of said arm. When the switch is released under these circumstances, although magnet 192 has been energized and deenergized, circuit changing spring 189 remains in its normal position, dog 360 holding arm 302 depressed until its lug passes to the right of the buffer on spring 189. This combination prevents movement of spring 189 when a calling subscriber releases after connecting with a line already in use. When armature 304 is attracted, arm 305 moves to the left and engages lugs 230 and 240 on detents 229 and 243 by means of orifices provided in the arm. In Fig. 11 is shown a top view of the operating end of arm 305. In the portion of Fig. 11 adjacent'thereto is shown the operating relations of lugs 240 and 230 to detents 243 and 229. \Vhen the armature is retracted, it draws the said detents out of engagement with the primary and secondary shafts, respectively. Associated with arm 305 is lever 231, provided with a roller as shown in Fig. 11. This lever, it will be remembered, is actuated upon the first movement of armature 232 of the primary magnet. Detents 230 and 240 are held by arm 305 in their retracted positions after the connector switch is returned to normal. The actuation of lever 231 causes the roller, shown in Figs. 8 and 11, at its extremity, to engage the bent portion of arm 305 which is thus raised, the arm disengaging lugs 230 and 240. The springs, shown in association with detents 229 and 243, then move them to en age their respective ratchets.

eferring to Fig. 12, when the detents are simultaneously withdrawn from the ratchets of the two shafts as described, spring 241, against the tension of which shaft 235 is operated, raises the shaft upward until it resumes the position shown,

in which the contact ends of the wipers are cation of drawings, cross references to Figs. I 6-12 Wlll be made in describlng selector switch mechanisms which, in conjunction with Figs. 13 and 11 illustrative of such Variations as exist, fully disclose the mechanisms required to perform the functions of the circhits shown at E and F'in' Fig. 1. Referring first to second selector switch circuit F, wipers 160, 161 and 162 are associated with a bank of contacts similar to that provided for the connector switch. Similar primary and secondary shafts are provided for operating the wipers. lrimary magnet 151 has mechanical parts associated with it such as magnet 176 of the connector switch has, and its operation with respect to them is the same. Secondary magnet 1&8 as plainly shown in Fig. 14 has operating parts like those of magnet 178 of the connector switch. Magnet 139 takes the place of magnet 179 on the switch mechanism, being provided with the switch spring combination shown in Fig. 1. Primary magnet 101 of the first selector switch circuit E is like primary magnet 176 ofthe connector switch; secondary magnet 119 is like magnet 148 of the second selector; and magnet 110 takes the place of magnet 179, being provided with the switch spring combination shown at Magnets of function similar to that of magnet 192 of the connector switch are not required for the selector switches.

Referring to Fig. 1+1, a side view of a second selector switch, it will be noted, first, that the normal position of the wipers, with reference'to the edge of the contact bank, is such that a first secondary step-by-step movement will cause it to engage the first set of contacts of a section. In the connector switch, two such movements were required. The first selector switch is similar to the second selector switch in this respect. Secondly, it will be noted that the spring combination of the second selector switch, operatedon the first movement of the primary shaft, varies from the corresponding combination of the connector switch. In this case, springs 132 and 135 engage springs 133 and 134 upon the first movement of the said shaft. The first selector switch is similar to the connector switch withrespect to this combination. 'lhirdly, the spring combination of the second selector switch, actuated on the first movement of the secondary shaft, varies from that of the connector switch. In this case, contacts 129128 and 13013l are broken. The first selector switch has here a spring combination similar to that of the second selector switch, comprising springs 92, 93, 94 and 95, shown in Fig. 1. Fourth,the secondary magnets of both selector switches are provided with vibratory circuits. Springs 149 and 150 in Fig. 141 are separated with each downward stroke of the armature of magnet 148, and again engage on the upward stroke. The same spring arrangement is provided for the first selector switch.

In Fig. 13 is shown the mechanism of a selector switch release magnet,the said magnet and its associated parts being for convenience provided with reference numbers corresponding to circuit F. The said mech anism is shown at normal. At 328 and 329 are shown the lugs of the detents of the primary and secondary shafts, respectively.

As shown, the detents will be out of en- 'gagement with their respective ratchets.

Lever 330 is actuated upon the first movement of the armature of the primary magnet (compare lever 231 of Fig. 11) and its roller engages the downwardly extending portion of rocker arm 326, the latter engaging release arm 327. The said arm is moved in an upward direction, so that lugs 328 and 32-9 are freed and the detents, of which they are part, move to engage the primary and secondary shafts, respectively. The right hand portion of rocker arm 396 moves downwardly, disengaging spring 136 whose tension causes the opening of contact 136-138 and the closing of contact 136-187. \Vhen release magnet 152 is energized, release arm 327 is drawn to the left and by two orifices. such as are shown in Fig. 11, engages lugs 328 and 329. \Vith the attraction of armature 158, arm 325 is drawn to the left and, engaging spring 136, moves it to the left to again close contact l36138. \Vhen this occurs, the lower end of the spring engages the tooth at the end of arm sac and the spring is held in the position shown until the next initial operation of the switch. When release magnet 152 is decnergized. armature 158 draws arm 327 to the right and lugs 328 and 329 are drawn with it, moving their respective detents out of engagement with the ratchets of the primary and secondary shafts. The shafts and their associated parts then return to normal, as described in connection with the shafts of the connector switch. Release magnet .102 of the first selector switch has operating 61 of control circuit D in Fig. 1; associated with relay 61 is a lever 343, provided with two studs 3-H and 345, as shown in Fig. 10. Hooked arm 3&0 normally engages lever 343. as shown, and the arm being normally held retracted, owing to its pivotal connection with the armature of relay 61, studs 3H and 3&5 maintain their respective spring combinations in the condition shown in Fig. 10. \Vhen relay ()0 is energized, its armature 342, pivotally connected to arm 341, lifts the said arm upward. The latter engages loosely the pin shown on arm 340, and the hook of said arm is raised to disengage lever 343. The tensions of. springs 14, 51, 86 and 89, acting upon studs 34% and 345, now push them and lever 343 to the right, and contacts 14-15, 5l53, 86-88 and 8991 are closed. lVhen, now, relay 61 is energized, its armature draws arm 340 to the right and its hook is brought to again engage lever 34.3. This movement of arm 3-l0 also closes contact 63 62, holding it closed as long as relay 61 continues energized. When the relay is deenergized, arm 3&0 is retracted, the said contact is again opened, and lever 343 is brought to its normal position shown, studs 3% and 345 causingtheir spring combinations to assume the normal conditions shownf My invention is not restricted to the application shown, comprising selector switches of two classes only, and in the claims I desire not to be limited in this respect. d

An off-normal switch is a switch adapted to be actuated on the first movement of an operating part, additional movements in the same direction as the first causing no further operation of the switch.

. I claim:

1. A telephone exchange system including manually operated impulse controlling mech anism, a relay at the exchange adapted to be controlled responsive to said mechanism, a step-by-step switch mechanism at the exchange including movable contact arms, an operating magnet for said arms, a second step-by-step switch mechanismv at the exchange including movable contact arms, an operating magnet for said arms, multipled terminals of trunking circuits arranged in groups, associated with each switch mechanism, adapted for use in establishing connections, a conductor adapted to transmit currents controlled by said relay, normally connected with the operating magnet of said first switch mechanism, and apparatus for disconnecting said conductor from said magnet and connecting it through to the operating magnet of said second switch mechanism.

2. A, telephone exchange system including manually operated impulse controlling mechanism, a relay atthe exchange adapted to be controlled responsive to said mechanism, a step-by-step switch. mechanism at the exchange including movable contact arms, an operating magnet for said arms. a second step-by-step switch mechanism at the exchange including movable contact arms. an operating magnet for said arms, multipled terminals of trunking circuits arranged in groups, associated with each switch mechanism, adapted for use in establishing connections, a conductor adznted to transmit currents controlled by said relay, normally connected with the operating magnet of said first switch mechanism, apparatus for disconnecting said conductor from said magnet and connecting it through to the operating magnet of said second switch mechanism, a second relay at the exchange adapted to be controlled responsive to said calling mechanism, apparatus for causing said first switch mechanism to select terminals of an idle trunking circuit, an electromagnet for said switch, controlling such selection, apparatus for causing said second switch mechanism to select terminals of an idle trunking circuit, an electromagnet for said switch, controlling such selection, a conductor adapted to transmit currents controlled by said second relay, normally connected with said second electromagnet of said first switch mechanism, and apparatus for disconnecting said conductor from said magnet and connecting it through to said second magnet of said second switch mechanism.

3. A telephone exchange system including manually operated impulse controlling mechanism, a relay at the exchange adapted to be controlled responsive to said mechanism, a step-by-step switch mechanism at the exchange including movable contact arms, a second step-by-step switch mechanism at the exchange including movable contact arms, multipled terminals of trunking circuits arranged in groups, associated with each switch mechanism, adapted for use in establishing connections, apparatus for causing said first switch mechanism to select terminals of an idle trunking circuit. an electromagnet for said switch, controlling such selection, apparatus for causing said second switch mechanism to select terminals of an idle trunking circuit, an electromagnct for said switch, controlling such selection, a conductor adapted to transmit currents controlled by said relay, normally connected with said electromagnet of said first switch mechanism, and apparatus for disconnecting said conductor from said magnet and connecting it through to said magnet of said second switch mechanism.

4. In an automatic telephone system. the combination with a telephone line connecting a substation with the exchange, calling mechanism at the substation controlled by the subscriber, an automatic switch at the exchange, adapted to be initially operated responsive to said mechanism, a single group of multipled terminals of trunking circuits, adapted to be engaged by said switch, means for arresting the operation of said switch when engaging a terminal of an idle circuit, a relay at the exchange, adapted to be controlled responsive to said calling mechanism when connection is made with an idle circuit, a step-by-step switch mechanism at the exchange including movable contact arms, an operating magnet for said arms, a second step-by-step switch mechanism at the exchange including movable contact arms, an operating magnet for said arms, multipled terminals of additional trunking circuits arranged in groups, associated with each switch mechanism, adapted to be used for establishing connections, a conductor adapted to transmit currents controlled by said relay, normally connected with the operating magnet of said first switch mechanism, and apparatus for disconnecting said conductor froni said magnet and connecting it through to the operating magnet of said second switch mechanism.

In anautomatic telephone system, the combination with a telephone line connecting a substation with the exchange, calling mechanism at the substation controlled by the subscriber, an automatic switch at the exchange, adapted to be initially operated responsive to said mechanism, a single group of multipled terminals of trunking circuits, adapted to be engaged by said switch, means for arrest-ing the operation of said switch when engaging a terminal of an idle circuit, a relay at the exchange, adapted to be controlled responsive to said calling mechanism when connection is made with an idle circuit, a step-by-step switch mechanism at the exchange including mov able contact arms, an operating magnet for said arms, a second step-by-step switch mechanism at the exchange including movable contact arms, an operating magnet for said arms. multipled terminals of additional trunking circuits arranged in groups, associated with each switch mechanism, adapted to be used for establishing connections, a conductor adapted to transmit currents controlled by said relay, normally connected with the operating magnet of said first switch mechanism, apparatus for disconnecting said conductor from said magnet and connecting it through to the operating magnet of said second switch mechanism, a second'relay at the exchange adapted to be controlled responsive to said calling mechanism when connection is made with an idle circuit, apparatus for causing said first switch mechanism to select terminals of an idle trunking circuit, an electromagnet for said switch, controlling such selection, apparatus for causing said second switch mechanism to select terminals of an idle trunking circuit, an electromagnet for said switch, controlling such selection, a conductor adapted to transmit currents controlled by said second relay, normally connected with said second electromagnet of said first switch mechanism and apparatus for dis connecting said conductor from said magnet and connecting it through to said second magnet of said second switch mechanism.

6. In an automatic telephone system, the combination with a telephone line connecting a substation'with the exchange, calling mechanism at the substation controlled by the subscriber, an automatic switch at the exchange, adapted to be initially operated responsive to said mechanism, a single group of multipled terminals of trunking circuits, adapted to be engaged by said switch, means for arresting the operation of said switch, when engaging a terminal of an idle circuit, a relay at the exchange, adapted to be controlled responsive to said calling mechanism when connection is made with an idle circuit, a step-by-step switch mechanism at the exchange including movable contact arms, a second step-by-step switch mechanism at the exchange including movable contact arms, multipled terminals of additional trunking circuits arranged in groups, associated with each switch mechanism, adapted to be used for establishing connections, apparatus for causing said first switch mechanism to select terminals of an idle trunking circuit, an electromagnet for said switch, controlling such selection, apparatus for causing said second switch mechanism to select terminals of an idle trunking circuit, an electromagnet for said switch, controlling such selection, a conductor adapted to transmit currents controlled by said relay, normally connected with said electromagnet of said first switch mechanism, and apparatus for disconnecting said conductor from said magnet and connecting it through to said n'iagnet of said second switch mechanism.

7. In an automatic telephone exchange system, the combination with a telephone line connecting a substation with the exchange, of an automatic switch individual to said line at the exchange including movable contact arms, multipled terminals adapted to be engaged by said arms, means for causing said switch, when initially operated from the substation, to select idle terminals, relays connected with said idle terminals, adapted to be operated by currents transmitted over said line by said calling mechanism, a first selector switch normally inoperative relation with said relays, mov-,

able cont-act arms for said switch, a plural ity of groups of second selector switches having terminals adapted to be engaged by said arms, movable contact arms for each 

